This invention relates to a dual power flow counter shaft transmission for a heavy duty work vehicle, and more particularly to a dual power flow counter shaft transmission having a plurality of forward and reverse speeds utilizing constant mesh gearing, a torque converter, and a plurality of fluid actuated rotating disc-type clutches so constructed and arranged as to provide maximum compactness and speed reduction ratio flexibility.
Counter shaft transmissions having a plurality of speed ratios in each direction of operation have been found to be particularly useful in the drive line of heavy duty work vehicles, such as wheel loaders, rubber tired log skidders and lift trucks. These transmissions are advantageous in that a plurality of rotating disc-type clutches and associated continually meshing gears can be so positioned on the usual parallel shafts as to allow considerable design flexibility and adaptability to the elevational drop requirement between the input and output axes.
One of the problems with these prior counter shaft transmissions is that they provide only a limited number of fixed gear ratios between the input and the output shaft. When operating at low speeds, these fixed gear ratios require a significant and abrupt change as one gear ratio is disengaged and the other gear ratio is engaged. While some of this abruptness can be eliminated by careful design of the clutch valve controllers, it cannot all be eliminated. In addition, by providing several closely spaced low range gear ratios, the work vehicle will spend a large amount of time shifting between those ratios to achieve the optimum gear ratio.
Accordingly, what is needed is a structurally simple, constant mesh counter shaft transmission that includes a torque converter that is engaged in a low range of gear ratios and is disengaged in a high range of gear ratios when the vehicle is operated at high speeds over the road.
The present invention is directed to providing such a transmission. In one embodiment of the invention, there is provided a dual power flow counter shaft transmission for a work vehicle that has an input shaft rotationally coupled to and driven by the vehicles engine. The input shaft has a first gear mounted for free rotation thereon and a first hydraulic clutch disposed to connect the first gear to the input shaft for conjoint rotation. A second gear is also mounted on the input shaft for free rotation thereon. A torque converter is disposed to couple the input shaft to the second gear to transmit power from the input shaft through the torque converter to the second gear, thereby driving the second gear.
A first counter shaft is also provided in the transmission and has a third gear mounted for free rotation thereon, a fourth gear mounted for free rotation thereon, and a fifth gear mounted for conjoint rotation with the first counter shaft. A second clutch is provided to connect the third gear with the first counter shaft. A third clutch is provided to connect the fourth gear to the first counter shaft. The first gear and the fourth gear are engaged to each other in continuous mesh. The fifth gear and the second gear are also engaged to each other in continuous mesh.
A second counter shaft is provided having a sixth gear mounted thereon for free rotation. A seventh gear is mounted on the third counter shaft for conjoint rotation. An eighth gear is mounted on the third counter shaft for conjoint rotation. A ninth gear is mounted on the third counter shaft for free rotation.
A fourth clutch is disposed on the second counter shaft to connect the sixth gear with the second counter shaft for conjoint rotation therewith. A fifth clutch is provided on the second counter shaft to connect the ninth gear with the second counter shaft for conjoint rotation therewith. The eighth gear and the fourth gear are in continuous meshing engagement.
A first output shaft is provided having a tenth gear mounted thereon for conjoint rotation. An eleventh gear and twelfth gear are mounted thereon for free rotation (with respect to the first output shaft) and for conjoint rotation (with respect to each other). A thirteenth gear is mounted on the output shaft for free rotation thereon and a fourteenth gear is mounted on the first output shaft for conjoint rotation therewith. A sixth clutch is disposed on the first output shaft to connect the eleventh and twelfth gears, which always rotate conjointly, to the first output shaft for conjoint rotation therewith. A fifteenth gear is mounted on the first output shaft for conjoint rotation therewith. A seventh clutch is disposed on the first output shaft to connect the thirteenth gear with the first output shaft for conjoint rotation therewith. The third gear on the first counter shaft is engaged with the twelfth gear on the first output shaft for continuous meshing engagement. The fourth gear on the first counter shaft is engaged to the eighth gear on the second counter shaft for continuous meshing engagement. The sixth gear on the second counter shaft is engaged with the tenth gear on the first output shaft for continuous meshing engagement. The seventh gear on the second counter shaft is connected to the eleventh gear on the first output shaft for continuous meshing engagement. The eighth gear on the second counter shaft is coupled to the thirteenth gear on the first output shaft for continuous meshing engagement. The ninth gear on the second counter shaft is coupled to the fourteenth gear on the first output shaft for continuous meshing engagement.
A mechanical front wheel drive output shaft is also provided having a sixteenth gear mounted for free rotation thereon. An eighth clutch is provided on the mechanical front wheel drive output shaft to connect the sixteenth gear to that shaft for conjoint rotation therewith.